﻿using System;
using System.Collections;

namespace Patterns.Iterator {
    public static class AbstractExample {

        public static void Run() {
            ConcreteAggregate a = new ConcreteAggregate();
            a[0] = "Item A";
            a[1] = "Item B";
            a[2] = "Item C";
            a[3] = "Item D";

            // Create Iterator and provide aggregate
            ConcreteIterator i = new ConcreteIterator(a);

            Console.WriteLine("Iterating over collection:");

            object item = i.First();
            while (item != null) {
                Console.WriteLine(item);
                item = i.Next();
            }
        }
    }

    // "Aggregate"
    abstract class Aggregate {
        public abstract Iterator CreateIterator();
    }

    // "ConcreteAggregate"
    class ConcreteAggregate : Aggregate {
        private ArrayList items = new ArrayList();

        public override Iterator CreateIterator() {
            return new ConcreteIterator(this);
        }

        // Property
        public int Count {
            get { return items.Count; }
        }

        // Indexer
        public object this[int index] {
            get { return items[index]; }
            set { items.Insert(index, value); }
        }
    }

    // "Iterator"
    abstract class Iterator {
        public abstract object First();
        public abstract object Next();
        public abstract bool IsDone();
        public abstract object CurrentItem();
    }

    // "ConcreteIterator"
    class ConcreteIterator : Iterator {
        private ConcreteAggregate aggregate;
        private int current = 0;

        // Constructor
        public ConcreteIterator(ConcreteAggregate aggregate) {
            this.aggregate = aggregate;
        }

        public override object First() {
            return aggregate[0];
        }

        public override object Next() {
            object ret = null;
            if (current < aggregate.Count - 1) {
                ret = aggregate[++current];
            }

            return ret;
        }

        public override object CurrentItem() {
            return aggregate[current];
        }

        public override bool IsDone() {
            return current >= aggregate.Count ? true : false;
        }
    }
}
